don't deal with pid files

we can't write out pid files since the code is using fork() and at
fork handler will delete the pid file.
make compile
add krb5_principal_is_root_krbtgt
make krb5_cc_get_lifetime sane
fixup
remove debug printf's
klist --json support
Update URL for Kerberos FAQ

Submitted by Trix Farrar <trix@basement.net> as FreeBSD PR 178417.
Merge pull request #25 from kaduk/faq

Update URL for Kerberos FAQ
Allow krb5_principal_set_realm to set the realm to NULL.
Reduce user surprise.  When PAM is configured to use a user_realm that
is different from the default realm, do likewise in kinit with bare
user names.

Qualify keytab principals with best realm from keytab, not the default realm.